Don't install MacKeeper, or any system utility on a Mac without first backing up your data
This user tip below on MacKeeper been cross posted on other Mac operating system forums.
https://discussions.apple.com/docs/DOC-3022
If you find a place that advertises it, please advise them it is not considered safe for use by Mac users.
Other third party system utilities that change system cache, fix the directory check for viruses, give you software firewalls, update pre binding, and affect DS_Store files can all be good in troubleshooting scenarios, but primary should only be used on backed up systems.
Many need constant updating to keep in sync with changes with the operating system.
System caches if modified at the wrong time can make applications unable to launch.
Here's what you need to know about backing up first: